Apparatus and Method in a Paper Machine and a Paper Machine

ABSTRACT

The invention comprises an apparatus and a method in a paper machine and a paper machine. According to the invention at least one deckle rail with strip form body of the forming table comprises openings for leading water between the deckle rail with strip form body and the stock layer and/or the deckle rail with strip form body and the wire.

TECHNICAL FIELD RELATED TO THE INVENTION

The object of the invention is an apparatus and a method in a paper machine and a paper machine according to the preambles of the independent claims presented below. The invention especially relates to an edge support of a forming table in a paper machine.

PRIOR ART

In a paper machine equipped with a flat forming table i.e. in a so-called Fourdrinier machine the stock layer flowing from the head box to the planar forming table must be supported by the edges. At this stage the fibre concentration of the stock is low, typically 0.3-0.8 weight-%, therefore its behaviour resembles the behaviour of water. Supporting of the edges is required to prevent the stock layer from running off the sides outside the wire area. Furthermore, without edge support the running off the sides causes flaws in the end product that are visible far away from the edge of the web, i.a. basis weight deficit, orientation discrepancy and tensile strength discrepancy. In FIGS. 1 a and 1 b a conventional edge support of a forming table according to prior art is shown. In FIG. 1 a there is shown a head box 1, fabric edge curler 2, an edge wave 3 indicated schematically by arrows and a deckle rail 4. In FIG. 1 b there is further shown a wire 5 and a wearing plastic lip 15 used for sealing Edge support according to prior art is thus usually comprised of a short rod-shaped deckle rail 4 on the wire and fabric edge curler 2 to be performed thereafter, in which with the aid of formed pieces the edge section of the wire 5 is lifted off the table, Drawbacks of a solution of this type are for example:

1. Fabric edge curler is located further out than the line of the deckle rail, in which case the ending of the rail causes a significant edge disturbance and a stock deficit, as material leaks out toward the edge of the wire.

2. Fabric edge curler reflects edge leakage inwards as an edge wave causing a downstream broadening edge disturbance in the machine direction.

3. No dewatering is directed at the fabric edge curler area, as the wire is not in contact with the table. This increases the stock imbalance of the edge area and impairs controllability.

4. Fabric edge curler functions differently when the driving parameters of the machine vary, such as the slice opening, machine speed and the underpressure of the dewatering. The disturbances caused by the fabric edge curler are thus difficult to remove in a machine that runs different grades.

5. The fabric edge curler stretches the wire causing a greater mechanical strain and thus faster wearing of the wire.

6. The deckle rail gets easily dirty, wherefore separate and often complicated washing solutions of the deckle rail have been developed.

THE AIM OF THE INVENTION AND BRIEF DESCRIPTION

The main object of the present invention is to reduce or even to eliminate the problems found in the prior art described above.

The primary aim of the present invention is to eliminate significant shortcomings and problems related to current edge support, whereby the section of a paper or board web that corresponds to the edge areas can be improved in terms of quality and in accordance with the operating values of the machine. The aim is to thus prevent the stock deficit caused by current technology and the leakage flow directed towards the edge of the wire in the edge areas of the web by extending the support of the deckle rail-type far downstream on the forming table. Such mechanical support requires, depending on the type of implementation, a reduction in friction between the stock and deckle rail by means of so-called lubricating water as well as the hydraulic sealing of the gap between the deckle rail and the wire by means of so-called sealing water.

An aim of the present invention is especially to achieve a paper or board machine, which produces paper or board of a better quality than before. It is also an aim to achieve a more economical and manageable edge support of a forming table in a paper machine. It is a further aim of the invention to achieve an arrangement, in which the surface friction between the stock and the edge support is lower than that of arrangements of prior art. Moreover an aim of the invention is to improve adjustability of the edge support.

In order to realise for instance the objects mentioned above the apparatus, method and paper machine according to the invention are characterised by what is presented in the characterising parts of the enclosed independent claims.

In this specification and in the claims the term paper machine is used in general terms. The term paper machine naturally also comprises board machines and other corresponding machines, which manufacture web from liquid containing stock.

A typical deckle rail of a forming table in a paper machine according to the invention comprises openings

-   -   in the inner edge of the deckle rail facing the wire in order to         lead water between the deckle rail and stock layer for the         lubrication thereof and/or     -   in the lower surface of the deckle rail in order to lead water         directly between the deckle rail and the wire, for the sealing         of the gap between the deckle rail and the wire with water.

In a typical method according to the invention in the paper machine stock is fed on the wire of the forming table of the paper machine to form a stock layer and the edges of the stock layer are supported by a deckle rail placed on the wire. It is also characteristic for a typical method that in the method water is transported inside the deckle rail and the space between the deckle rail and the stock layer is lubricated by leading water from inside the deckle rail between the deckle rail and the stock layer, and/or the gap between the deckle rail and the wire is sealed by leading water from inside the deckle rail between the deckle rail and the wire. In a typical method water can also be led outside the deckle rail, from where it can be divided by means of a manifold, hoses or branching pipe to different parts of the deckle rail, from where it is further led between the deckle rail and stock layer and/or deckle rail and wire. In connection with a method according to the invention no fabric edge curler is required, however, it can nevertheless be used.

BRIEF DESCRIPTION OF THE FIGURES

FIGS. 1 a and 1 b show a conventional edge support of a forming table according to prior art,

FIGS. 2 a and 2 b show the basic features of hydrodynamic edge support according to a first embodiment of the invention,

FIG. 3 shows a deckle rail according to a second embodiment of the invention,

FIGS. 4 a and 4 b show a deckle rail according to a third embodiment of the invention,

FIG. 5 shows a deckle rail according to a fourth embodiment of the invention as well as dewatering,

FIGS. 6 a and 6 b of show transportation of water to the deckle rail according to a fifth embodiment of the invention, and

FIGS. 7 a and 7 b show feeding of sealing water from the end of the deckle rail according to a sixth embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The embodiments and advantages mentioned in this text relate both to the apparatus, the method as well as to the paper machine according to the invention, where applicable, even though it is not always specifically mentioned.

The invention relates to an apparatus in a paper machine, which apparatus comprises at least one deckle rail for supporting the edge of the stock layer on the wire of the forming table as well as means for leading water to the vicinity of the deckle rail. A typical deckle rail of a forming table in a paper machine according to the invention further comprises openings or gaps in the inner surface of the deckle rail facing the wire for leading water between the deckle rail and the stock layer in order to lubricate this space and/or in the lower surface of the deckle rail for leading water directly between the deckle rail and the wire in order to seal the gap between the deckle rail and the wire with water.

According to an advantageous embodiment of the invention there are at least two deckle rails, one of which is typically in the machine direction on both sides of the stock layer arranged on the wire so that the stock layer can be supported on both sides. There can be for example 1, 2, 3, 4, 5, 6, 7, 9 or 12 deckle rails on both sides of the wire. In this application by supporting the stock layer can also be meant limiting the stock layer.

The deckle rail according to one embodiment of the invention can be made of plate, in which has been arranged openings or gaps by boring or otherwise. Openings arranged in the inner side of the deckle rail facing the wire for feeding lubricating water can have a diameter of for example 1-5 mm. When using elongated gaps the height of the gaps can be for example 1-2 mm. Openings arranged in the lower surface of the deckle rail for feeding sealing water can have a diameter of for example 3-10 mm. When using elongated gaps the height of the gaps can be for example 2-8 mm.

The inner side of the deckle rail facing the wire and the lower surface according to the invention can typically be of a porous material, the structure of which comprises a large number of small openings. When using a porous material the water flow is distributed particularly evenly on the entire surface area of the porous material. The surface of the porous material is easily kept clean and lubrication and sealing function particularly well.

The deckle rail can be made of ceramics, metal or plastic, for example,

The basic features of typical hydrodynamic edge support according to the invention are thus:

-   -   The support does not normally involve fabric edge curler, i.e.         lifting the wire up from the table, as fabric edge curler is not         required in a solution according to the invention, Fabric edge         curler is, however, possible to use in connection with a         solution according to the invention.     -   The support is based on an element like the deckle rail, which         can also be called a hydrolimiter.     -   The deckle rail comprises openings in the inner edge surface of         the deckle rail facing the wire for leading the water between         the deckle rail and the stock layer in order to lubricate this         space and/or in the lower surface of the deckle rail for leading         water directly between the deckle rail and the wire in order to         seal the gap between the deckle rail and the wire with water.     -   Dewatering extends at least substantially to the entire width of         the web. Advantageously the dewatering only extends to the inner         surface of the deckle rail, whereby dewatering does not take         place from underneath the rail, and thus the required amount of         sealing water remains low and easier manageable. It is, however,         possible to extend the dewatering underneath the deckle rail.

The greatest improvements to current paper machines equipped with flat forming tables which can be attained with the aid of a deckle rail according to the invention, which also can be called a hydrolimiter, are:

-   -   The width of the machine can be nearly maximally utilised         because of the very small edge disturbance. Typically, depending         on each case, a 10-60 cm wider web than at present of good         quality can be attained.     -   Due to smaller edge disturbances web breaks decrease.     -   Dewatering is directed evenly on the entire width of the web all         the way to the deckle rails. Thus smaller discrepancies in basis         weight and more even drying properties are achieved.     -   As the wire does not need to be lifted by its edges, there is         less strain on the wire.     -   The function of the deckle rail can be adjusted by changing the         flows of its lubricating water. Differing from current edge         support and its difficult adjustability the function of the         deckle rail according to the invention can easily be adjusted         also as an operation when the machine is running. Quality         specific adjustments to the deckle rail for different products         can be arranged, if necessary, to function automatically and can         be advantageously realised as a flow adjustment.     -   Means for feeding water can be arranged at the end of the deckle         rail in the machine direction and according to possibility at         machine speed as well as at the thickness of the stock layer.         Water fed in this manner supports the stock layer after the end         of the deckle rail and prevents the stock from spreading out         towards the outer edge of the wire.

Advantageously the deckle rail is long, extending almost from the head box almost to the dry line, The deckle rail or a combination of deckle rail elements can regarding its length be for example 30-100% of the length of the forming table, advantageously 50-99% of the length of the forming table. An arrangement according to the invention can for example start immediately at the end of the forming table or at a distance of about 1-50 cm therefrom, The arrangement can likewise end at the dry line or in the vicinity thereof.

As paper machines are individual, different embodiments of the central element of the hydrodynamic edge support according to the invention, the deckle rail, are conceivable. Certain such separately or as combinations implemented solutions are:

-   -   a) The deckle rail is long, extending to such a measure, in         which a remarkable part of the dewatering of the table has         occurred and there is a filtered layer on the wire, which layer         also can be called a fibre layer as the relative fibre content         of the layer has remarkably grown, as a consequence of         dewatering.     -   b) The deckle rail functions as a channel for lubricating and         sealing water.     -   c) The gap between the deckle rail and the wire is sealed with         sealing water, whereby the sealing is achieved in the manner of         a hydrodynamic sealing by bringing underneath the deckle rail         water having a smaller pressure loss and therefore a leakage         flow towards the stock layer. Sealing water can be brought         through suitable openings from inside the actual deckle rail.         There can be arranged on the lower surface of the deckle rail         lamelIa or the like for creating suitable pressures and flows.         The lower surface of the deckle rail can be of a porous         material, structure of which comprises a large number of small         openings. Naturally also other manners of feeding sealing water         are possible.     -   d) The inner surface of the deckle rail is fed with sealing         water, by means of which the surface is kept clean and the         surface friction low. Thus the boundary layer forming on the         surface of the deckle rail is thin and the disturbance extending         to the web insignificant. This is an especially important         feature when the deckle rail extends near the dry line. The         lubricating water can, for example, be brought through suitable         openings from inside the actual deckle rail in the manner as         described below in more detail by the figures. The feeding         openings can be on the inner surface of the deckle rail, whereby         the lubricating water is effectively fed directly between the         deckle rail and the stock layer. The inner surface of the deckle         rail can be for example of a porous material, the structure of         which comprises a large number of small openings. Naturally also         other manners of feeding lubricating water are possible.     -   e) The filtered layer forming on the wire and the flow         resistance thereof can be used for sealing the gap between the         lowver surface of the deckle rail and the wire, especially at         the last section of the deckle rail. Increasing the gap between         the deckle rail and the wire relative to the thickness of the         filtered layer is used as implementation. In some cases a simple         sealing plate or sealing arranged on the outer edge of the rail         can be utilised as well.

According to the invention the inner surface of the deckle rail is kept clean and the surface friction low with the aid of the lubricating water. Consequently the stock, layer hardly attempts to stick to the surface of the deckle rail.

The deckle rail according to the invention can be formed by one long element or it can be formed by several shorter elements connected to each other. Connecting the elements to each other can be performed by any per se known method to someone skilled in the art. The function of the deckle rail according to the invention can vary in different locations, for example the amount of lubricating water to be fed can differ according to need in different parts of the forming table. An advantageous deckle rail according to the invention is substantially parallel or as parallel as possible with the travel direction of the wire. Thus, the formation of edge waves can be minimised.

The invention also relates to a method in a paper machine. In a typical method according to the invention in the paper machine stock is fed on the wire of the forming table of the paper machine to form a stock layer and the edge of the stock layer is supported by at least one deckle rail placed on the wire. It is also characteristic for a typical method that in the method water is brought inside the deckle rail and the space between the deckle rail and stock layer is lubricated by leading water from inside the deckle rail between the deckle rail and the stock layer, and/or the gap between the deckle rail and the wire is sealed by leading water from inside the deckle rail between the deckle rail and the wire.

According to an embodiment of the invention the lubricating water is led through the inner edge of the deckle rail facing the wire directly between the deckle rail and the stock layer, whereby the advantages described above and below are attained.

According to another embodiment of the invention the sealing water is led through the lower edge of the deckle rail facing the wire directly between the deckle rail and the wire.

According to yet another embodiment of the invention water from the end of the deckle rail is fed substantially in the machine direction in order to support the edge of the stock layer arranged on the wire.

The invention also relates to a paper machine comprising a forming table which is characterised by an apparatus according to an embodiment of the invention in connection with the forming table.

Advantageously the means for bending the edges of the wire upwards are lacking from the forming table of such a paper machine, that is as the arrangement described above is used, there is no need to bend the edges of the wire upwards. In connection of the forming table there can be means for bending the edges of the wire upwards and the edges of the wire can be bent upwards, if it is considered necessary.

The invention is described in more detail below with reference to the enclosed schematic drawing.

DETAILED DESCRIPTION OF THE FIGURES

In FIGS. 1 a and 1 b an arrangement according to prior art is shown, which has been described above, i.e. conventional edge support of a forming table.

FIGS. 2 a and 2 b show the basic features of hydrodynamic edge support according to the first embodiment of the invention. In FIG. 2 a an arrangement is shown according to an embodiment of the invention as seen from above. The arrangement comprises a head box 1, a wire section 6, a dewatering area 7 and a deckle rail 8 according to an embodiment of the invention. In FIG. 2 b a section of the arrangement in FIG. 2 a is shown as seen from the end, and in particular the deckle rail 8 and the wire 5 have been depicted therein.

In FIGS. 2 a and 2 b it is shown a basic feature of typical hydrodynamic edge support according to the invention, that is that the support does not include fabric edge curler, that is raising the wire from the table, but is based on an element such as the deckle rail.

The deckle rail shown in FIG. 2 a is long extending to such a distance from the head box, that a significant part of the dewatering taking place on the forming table has been effected and there is a filtered layer of paper or board stock on the wire.

FIG. 3 shows a deckle rail according to a second embodiment of the invention and the rail/laminated structure thereof as well as the use of sealing water for sealing. In this solution the deckle rail 8 functions as a channel for lubricating water (indicated by arrows 9) and the gap between the deckle rail 8 and the wire 5 is sealed by sealing water. Also stock 10, which can be paper or board stock, is schematically shown in the figure. Sealing is achieved in the fashion of a hydrodynamic sealing by bringing underneath the deckle rail 8 water having a smaller pressure loss and therefore the leakage flow towards the stock layer 10. Advantageously the sealing water is brought in the manner shown in FIG. 3 through suitable gaps from inside the actual deckle rail 8. In this embodiment the lower surface of deckle rail 8 has lamellas 11. By using lamellas 11 of different heights, the gap between the deckle rail 8 and the wire 5 can be altered and thus suitable pressure and flow conditions can be achieved.

FIGS. 4 a and 4 b show a deckle rail 8 according to a third embodiment of the invention and an example of how the surface of the deckle rail 8 is kept clean with sealing water 12 according to the invention and surface friction low in relation to the non-lubricated flow. Consequently, the stock layer 10 hardly attempts to stick to the surface of the deckle rail 8.

Even in this embodiment the deckle rail 8 functions as a channel to sealing water (shown schematically by arrow 12). FIGS. 4 a and 4 b describe the situation in the last section of the deckle rail 8, in which for sealing the gap between the lower surface of the deckle rail 8 and the wire 5 a filtered layer 13 formed on the surface of the wire 5 and the flow resistance thereof can be used. Additionally the figures show the stock 10 on the filtered layer 13. In an embodiment according to FIG. 4 a the feeding openings for sealing water are arranged on the inner surface 14 of the deckle rail 8, whereby the lubricating water 12 is efficiently fed directly between the deckle rail 8 and stock layer 10. In FIGS. 4 a and 4 b also lubricating water layer 16 and the lamellas 11 on the lower surface of the deckle rail 8 are shown.

In FIG. 4 b yet another alternative embodiment has been shown, in which the gap between the deckle rail 8 and the wire 5 has been increased relative to the thickness of the filtered layer 13. In the embodiment of FIG. 4 b the inner surface 14 b of the deckle rail is of a porous material, the structure of which comprises a large number of small openings. While using a porous material the feeding of lubricating water 12 is distributed particularly evenly and the inner surface 14 b of the deckle rail is kept very clean.

A deckle rail 8 and a suction box 17 for dewatering according to a fourth embodiment of the invention are shown in FIG. 5. In the example according to the figure suction box 17 ends at the inner line of the deckle rail 8, so that dewatering does not take place from underneath the deckle rail 8. whereby the amount of sealing water can more closely be controlled and it easily remains low. In solutions according to prior art dewatering extends often outside the line defined by the deckle rail.

FIGS. 6 a and 6 b show an example according to a fifth embodiment of the invention of how the transport of water to the deckle rail 8 can be arranged. In the example in FIG. 6 a water is transported to the deckle rail 8 by a tube 18 a, which has branches 18 b. In the example in the FIG. 6 b the tube 18 a has a bypass manifold, from which water flows along hoses 18 c to the deckle rail 8.

FIGS. 7 a and 7 b show the feeding of sealing water 19 at the end of the deckle rail 8 according to the sixth embodiment of the invention. Sealing water 19 is fed substantially in the machine direction and according to opportunity at machine speed for supporting the edge of the stock layer 10 on the wire 5. A raised deckle rail 8 according to FIG. 7 b is particularly well suited to a situation where the filtered layer 13 on the wire 5 is significant. In the example of the figure the lower edge of the deckle rail 8 ends at a point, where sealing water 19 is fed. The upper edge of the deckle rail 8 continues further forward from the feeding point of sealing water 19, which solution can be called a raised deckle rail. According to the example of the figure the thickness of the filtered layer grows in the machine direction at the same time as the stock layer becomes thinner, Only advantageous embodiments according to the invention have been presented in the Figures. It is apparent to someone skilled in the art that the invention is not limited exclusively to the examples described above, but that the invention can vary within the scope of the claims presented below and what has been disclosed in the specification. The dependent claims present some possible embodiments of the invention, and they are not to be considered to restrict the scope of protection of the claims as such. Also the reference numbers are not to be considered to restrict the scope of protection of the claims. Further the verb “comprise” is to be interpreted as open. 

1. Apparatus in a paper machine, comprising at least one deckle rail (8) for supporting the edge of a stock layer (10) on a wire (5) of a forming table, means for leading water to the vicinity of the deckle rail (8), characterised in that the apparatus comprises openings in the lower surface of the deckle rail (8) for leading water directly between deckle rail (8) and the wire (5), for the sealing of the gap between the deckle rail (8) and the wire (5) with water.
 2. Apparatus according to claim 1, characterised in that, it comprises openings in the Inner edge of the deckle rail (8) facing the wire for leading of water between the deckle rail (8) and the stock layer (10) for lubricating of this gap.
 3. Apparatus according to claim 1 or 2, characterised in that, the inner edge of the deckle rail facing the wire and/or the lower surface of the deckle rail is of a porous material.
 4. Apparatus according to any of the claims 1-3, characterised in that, at the end of the deckle rail means have been arranged for feeding water substantially in the machine direction for supporting the edge of the stock layer on the wire.
 5. Apparatus according to any of the claims 1-4, characterised in that, the deckle rail (8) is substantially long, comprising the majority of the length of the forming table, extending at least nearly from the head box (1) at least nearly to the dry line.
 6. Method in a paper machine, in which stock is fed to the wire (5) of the forming table in a paper machine to form a stock layer, the edge of the stock layer (10) is supported by at least one deckle rail (8) on the wire (5), characterised in that, in the method water is brought inside the deckle rail (8) and the space between the deckle rail (8) and the wire (5) is sealed with water by leading water from inside the deckle rail (8) between the deckle rail (8) and the wire (5).
 7. Method according to claim 6, characterlsed In that, the gap between the deckle rail (8) and the stock layer (10) is lubricated by leading water from inside the deckle rail (8) between the decide rail (8) and the stock layer (10).
 8. Method according to claim 7, characterised in that, the lubricating water is led through the inner surface of the deckle rail (8) facing the wire directly between the deckle rail (8) and the stock layer (10).
 9. Method according to any of the claims 6-8, characterised in that, the sealing water is led through the lower surface of the deckle rail (8) facing the wire directly between the deckle rail (8) and the wire (5).
 10. Method according to any of the claims 6-9, characterised in that, in the method dewatering takes place substantially on the entire width of the web, extending to the inner surface of the deckle rail.
 11. Method according to any of the claims 6-10, characterised in that, in the method water (19) from the end Of the deckle rail (8) is fed substantially in the machine direction for supporting the edge of the stock layer (10) on the wire (5).
 12. Paper machine, comprising a forming table, characterised in that, in connection with the forming table is an apparatus according to any to the claims 1-5.
 13. Paper machine according to claim 12, characterised in that, the forming table lacks means for bending the edges of the wire (5) of the forming table upwards. 